1. Field of the Invention
Implementations described herein relate generally to devices and, more particularly, to a flexible circuit to board connector.
2. Description of Related Art
Printed circuit boards (PCBs) (which may be referred to as printing wiring boards (PWBs) or etched wiring board assemblies) may be used in computers, communications devices (e.g., pagers, personal digital assistants (PDAs), telephones, etc.), televisions, cameras, and/or many other devices. In a typical PCB, many electrical components may be attached to the top and/or bottom surfaces of the PCB. PCBs may be used to mechanically support and electrically connect the many electrical components using conductive pathways, or traces, which may be etched from copper sheets laminated onto a non-conductive substrate.
Flexible circuits (which may be referred to as flexible printed circuits (FPCs)) may also be used in the devices described above in connection with PCBs. Flexible circuits may be formed by depositing electrical components on flexible substrates (e.g., thin, flexible plastic or metal foil substrates). In the simplest case, a flexible circuit may be made using the same or similar electrical components used for rigid PCBs, but the substrate may be made flexible instead of rigid. Flexible circuits may be used as connectors in devices where flexibility, space savings, or production constraints limit the serviceability of rigid PCBs. Flexible circuits may be ideal for highly compact products because they may be shaped as desired. Flexible circuits may be effective in preventing incorrect wiring and may reduce wiring costs.
Many devices may incorporate a combination of PCBs and/or flexible circuits. A flexible circuit may interconnect with a PCB(s) in such devices. Electrical interconnects may be used in the majority of all electronic packages, and usually more than once. Electrical interconnects may have the greatest single impact on the ease of assembly and disassembly of an electronic device. For example, the need to produce several million units of a given cellular product (e.g., cellular phone) design per year may necessitate cost-effective and reliable solutions for electrical interconnects.
Currently, PCBs may electrically interconnect to flexible circuits using low insertion force (LIF) or zero insertion force (ZIF) connectors. However, pressure may deform the securing arms of the electrical contacts of a ZIF connector, and/or may displace the electrical contacts. When this happens, the ZIF connector may not provide reliable electrical connection between the flexible circuit and the PCB.
PCBs may also electrically interconnect to flexible circuits using surface mount, pin board to board (BTB) connectors. While BTB connectors may offer certain benefits, they are very unforgiving of tolerance, especially in the (XY) plane of a PCB.
Another type of electrical interconnect may be a ball grid array (BGA). In a BGA, balls of solder may cover (or partially cover) a portion of a PCB in a grid pattern. A flexible circuit may include contacts or pads arranged to match the grid pattern of the BGA. The arrangement may be heated, causing the solder balls to melt. Surface tension may cause the molten solder to hold the PCB in alignment with the flexible circuit, while the solder cools and solidifies. Unfortunately, the solder balls in BGAs may not flex sufficiently, so that bending and thermal expansion of the PCB may be transmitted directly to the flexible circuit. This may cause solder joints to fracture under high thermal or mechanical stress. Another disadvantage of BGAs may be the difficulty in locating soldering faults once soldering is complete.
A further type of electrical interconnect may be a pin grid array (PGA). A PGA may be similar to a BGA, but pins (instead of balls of solder) may cover (or partially cover) a portion of a PCB in a grid pattern. The pins may be used to conduct electrical signals from a circuit (e.g., a flexible circuit) to a PCB to which the circuit may be connected, e.g., via soldering. PGAs may be produced with more and more pins, and with decreasing spacing between the pins, which may cause difficulties for the soldering process. As the pins get closer together, the danger of accidentally bridging adjacent pins with solder may grow.
Another significant disadvantage of LIF, ZIF, and BTB connectors, and BGA and PGA soldering is that such electrical interconnects may be expensive. This may be a distinct disadvantage in today's world of high volume, low cost electrical devices.